Graded GaAsSb strain reducing layers covering InAs/GaAs quantum dots

We have grown new InAs/GaAs quantum dot (QD) structures with graded Sb concentration of GaAs(1−x)Sbx strain reducing layer (SRL). New types of GaAsSb SRLs with graded concentration of Sb are theoretically and experimentally studied. We compare properties of three different Sb concentration gradients in SRL, constant, increasing and decreasing during the growth. Both types of non-constant gradients help us to prevent transition of the InAs(QD)/GaAsSb(SRL) heterojunction from type I to type II, to increase emission wavelength and to retain high luminescence intensity of these types of QD structures. Comparison of photoluminescence of samples with different concentration gradients and similar average Sb concentration in SRLs is shown. The longest wavelength of type I ground state transition was achieved on sample with decreasing gradation of Sb content in SRL—1399 nm (0.886 eV).

► We suggest new types of graded GaAsSb strain reducing layers covering InAs/GaAs QDs. ► The longest photoluminescence wavelength was achieved for decreasing Sb gradient in SRL. ► We achieved type I ground state transition at 1399 nm, FWHM 35 meV and intense RT PL. ► The experimental data were in agreement with theoretically expected behavior.